Restrictive Lung Diseases

Question 1

Definition of restrictive lung diseases

Answer 1

• diffuse parenchymal lung disease, acute or chronic
• characterised by widespread inflammatory pathology predominantly in the interstitium
• reduced expansion of lung parenchyma due to decreased compliance (edema, fibrosis)
• decreased total lung capacity
• normal expiratory flow rate

Question 2

Examples of restrictive lung diseases

Answer 2

1. Acute/Adult respiratory distress syndrome

2. Chronic interstitial lung disease

Question 3

Features of ARDS

Answer 3

• severe form of acute lung injury (acute diffuse parenchymal disease)
• clinical syndrome caused by diffuse alveolar & capillary damage
• high mortality/morbidity

Question 4

Causes of ARDS

Answer 4

• systemic sepsis
• severe trauma/burns
• inhalation of toxic fumes

Question 5

Outcomes of ARDS

Answer 5

1. Death in acute phase (70%)
2. Healing - regeneration of type II alveolar lining cells + inflammation of interstitium - organisation - fibrosis
   (A) recovery w minimal residual resp dysfunction (10%)
   (B) marked interstitial fibrosis (honeycomb lung) - death due to chronic severe resp impairment (20%)

Question 6

Pathogenesis of ARDS (3)

Answer 6

1. Damaging stimulus to lung, alveolar lining cells, alveolar capillary endothelium
2. Acute exudative phase
   - interstitial edema & high protein exudation into alveoli (fibrin rich fluid + necrotic epithelial cells = hyaline membranes)
   - alveoli damaged + edema - no gas exchange - resp failure
3. Late organisation phase
   - regeneration of type II alveolar lining cells
   - organisation of hyaline membranes w fibrosis
   - interstitium gets fibrotic, granulation tissue - lungs non compliant - increased O2 diffusion distance

Question 7

Outcomes of chronic interstitial lung disease

Answer 7

1. Honeycomb lung
   - end stage chronic pulmonary fibrosis
   - alveoli destroyed, looks bigger, thicker septum due to fibrosis
   - leads to chronic resp impairment & reduced diffusion capacity
   - resp + cardiac failure

Question 8

Causes of chronic interstitial lung disease (7)

Answer 8

1. Idiopathic
2. Hypersensitivity
3. Pneumoconiosis
4. Sarcoidosis
5. Complication of atypical pneumonia
6. Connective tissue diseases
7. Drug-induced, radiation damage, smoking related

Question 9

Features of hypersensitivity pneumonitis/extrinsic allergic alveolitis

Answer 9

• Farmer’s lung, bird fancier’s disease, humidifier lung
• Acute exposure - type III hypersensitivity response (acute illness)
• Repeated exposure - sensitisation & type IV hypersensitivity reaction (chronic, progressive illness, resulting in pulm fibrosis )

Question 10

Features of pneumoconiosis

Answer 10

• lung disease caused by inhalation of dust
• interaction of dust w defence mechanisms of lung - inflammation, cytokine release - stimulate fibrosis
• silica, coal dust, asbestos